Plasma and Fusion Research

Volume 14, 2405014 (2019)

Regular Articles

Examination of Bunching Effect of Dual-Frequency Modulation in a Traveling Wave Direct Energy Converter Simulator
Hiromasa TAKENO, Hiroki SATO, Kazuhiro SHIBATA, Kazuya ICHIMURA and Yousuke NAKASHIMA1)
Graduate School of Engineering, Kobe University, Kobe 657-8501, Japan
Plasma Research Center, University of Tsukuba, Tsukuba 305-8577, Japan
(Received 26 September 2018 / Accepted 30 November 2018 / Published 24 January 2019)


As for traveling wave direct energy converter (TWDEC), which was expected to be used for energy recovery of fast protons in D-3He fusion, a new modulation scheme was proposed for better bunching. An analytical formula was derived for complete bunching as an ideal waveform, and use of dual-frequency was proposed for practical application. In the scheme, independent two modulation electrodes were used and applied voltages were obtained by Fourier components of the fundamental and the second harmonic frequencies of the ideal waveform with taking running time between electrodes into account. The effect was confirmed by numerical orbit calculation, and improvement of bunching was found even for the ion beam with energy spread. The effect was indirectly confirmed experimentally by comparing variation of the third harmonic signal with an equivalent value in the orbit calculation. The optimum amplitude of the second harmonic frequency was discussed by comparing the composed waveform with the ideal one.


advanced fusion, direct energy conversion, TWDEC, modulator, dual-frequency modulation

DOI: 10.1585/pfr.14.2405014


  • [1] H. Momota, LA-11808-C, Los Alamos Natl. Lab., 8 (1990).
  • [2] M. Ishikawa et al., Fusion Eng. Des. 41, 541 (1998).
  • [3] H. Katayama and K. Sato, J. Plasma Fusion Res. 77, 698 (2001) (in Japanese).
  • [4] H. Takeno et al., Jpn. J. Appl. Phys. 39, 5287 (2000).
  • [5] Y. Togo et al., Plasma Fusion Res. 10, 3405013 (2015).